1. Field of the Invention
This invention relates to processes for producing polyamide foam.
2. Description of the Prior Art
Polyamide foam has recently been produced by polymerizing a lactam in the presence of a basic catalyst, an activator and a foaming agent, but the prior process has not been used on a commercial basis on account of a number of disadvantages. First, the polymerization foaming temperature is high, at least higher than 130.degree. C., and preferably higher than 150.degree. C., and even at these temperatures the rate of polymerization is low.
Secondly, the volume of foam produced is relatively small, and accordingly the foam produced has a high density with very limited use. The production of such foam is further complicated since the polymerization should be performed in the absence of moisture under an inert gas atmosphere. Finally, the cost of such foam is very high since special compounds are required as activators.